JP2002060542A - Method for recovering useful component from polyester waste - Google Patents

Abstract

PROBLEM TO BE SOLVED: To establish a method for effectively recovering EG and DMT as useful components from polyester wastes including natural fibers. SOLUTION: A natural fiber containing wasted polyester is treated under conditions under which the natural fibers substantially do not fuse and/or decompose. The polyalkylene terephthalate is depolymerized with EG, and the natural fibers are removed as a solid matter by solid liquid separation. The polyalkylene terephthalate containing EG solution drawn out from the liquid side of the solid liquid separation is treated with MeOH to recover DMT and EG.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for recovering active ingredients from polyester waste, and more particularly, to a method for recovering active ingredients from polyester waste.
The present invention relates to a method for efficiently separating and recovering dimethyl terephthalate and ethylene glycol as active ingredients from polyester waste substantially consisting of polyalkylene terephthalate and natural fibers.

[0002]

2. Description of the Related Art Polyalkylene terephthalate is excellent in chemical stability, and thus is useful for fibers, films,
It is produced and used in large quantities in food-related fields such as living-related materials such as resins, drinking water, and carbonated beverage bottles.

[0003] However, wastes of fibers, films, resin products and non-standardized polyalkylene terephthalates (hereinafter referred to as “polyalkylene terephthalates”), which are generated in large quantities with an increase in production and use, are called.
Sometimes simply abbreviated as polyester waste. The processing costs described in item (1) are not only related to the product costs, but also these types of processing are currently a major social problem, and various proposals have been made for recycling methods.

[0004] However, while material recycling, which converts polyester waste to lower quality grades by melt molding, has greatly improved the so-called "disposable" situation, the resulting recycled products can be further recycled when recycled. The use of polyalkylene terephthalate is ultimately difficult to avoid because of its reduced use.

[0005] Thermal recycling using polyester waste as fuel has also been carried out. Although this method has the advantage of reusing the combustion heat of polyester waste, it has no other choice but to burn off the polyester waste.Therefore, there is a problem of loss of the polyalkylene terephthalate raw material and generation of carbon dioxide. It is not preferable from the viewpoint of global environmental protection.

On the other hand, with respect to the above two kinds of recycling methods, a chemical recycling method of converting and recovering polyester waste into its constituent components, producing a polyalkylene terephthalate by a polymerization reaction again, and reusing the same is also being studied.

That is, the recovered polyester waste is reacted with methanol (hereinafter sometimes abbreviated as MeOH), and dimethyl terephthalate (hereinafter sometimes abbreviated as DMT) and a chemical recovered as alkylene glycol. Recycling basically recycles and reuses compounds without loss, so that the originally intended resource can be reused.

[0008] However, polyester waste discharged from the distribution industry and households includes not only resins and films, but also fiber waste in the form of fibers usually blended with natural fibers (mainly blended with cotton and hemp). Often discarded.

The mixed natural fibers are decomposed in the course of heating operation and reaction operation of the polyester waste, and may cause damage to equipment, generation of offensive odor, and other problems. Further, the decomposition product may significantly reduce the quality of the recovered DMT and alkylene glycol. For this reason, in the above-mentioned chemical recycling, in order to effectively utilize the polyester waste, it is necessary to separate natural fibers contained therein.

Conventionally, as a method for recovering polyester waste, a method is known in which polyalkylene terephthalate is depolymerized with ethylene glycol (hereinafter sometimes abbreviated as EG) and then transesterified with MeOH to obtain DMT. Is widely known as a glycolysis-transesterification reaction method, and is industrially practiced.

However, the thermal decomposition temperature of natural fibers is
Since animal fibers are as low as about 130 ° C. and plant fibers are as low as about 200 ° C., the chemical recycling of polyalkylene terephthalate containing natural fibers due to the thermal decomposition of natural fibers in the above-mentioned glycolysis method usually performed at 200 to 240 ° C. , Its application was difficult. For this reason, a method of dissolving and separating polyester into aromatic esters such as dimethyl terephthalate, methyl paratoluate and dimethyl isophthalate (US Pat. No. 5,866,622) has been proposed. Polyester waste, which is problematic and essentially contains natural fibers, is usually
At present, it is separated from other polyester waste by pre-treatment, and no chemical recycling is performed.

[0012]

SUMMARY OF THE INVENTION An object of the present invention is to solve the problems of the prior art and to convert DMT and EG from polyester waste consisting essentially of natural fibers and polyalkylene terephthalate. The purpose is to establish a method for efficient collection.

[0013]

Means for Solving the Problems The present inventors have made intensive studies in view of the above-mentioned prior art, and as a result, have found that polyester waste can be produced at a temperature that does not cause problems such as thermal decomposition of natural fibers by using a catalyst. The present inventors have found that if depolymerized with EG, the mixed natural fiber can be left as a solid substance and can be easily separated and recovered, and the present invention has been completed.

That is, an object of the present invention is a method for separating and recovering an active ingredient from a polyester waste substantially consisting of natural fibers and polyalkylene terephthalate, wherein the waste is separated into the following (a) to (c): Characterized by separating and recovering dimethyl terephthalate and alkylene glycol as active ingredients,
This can be achieved by a method for recovering active ingredients from polyester waste. (A) A step of charging polyester waste into ethylene glycol containing a depolymerization catalyst at a temperature of 110 to 210 ° C. (B) a step of removing the natural fiber by solid-liquid separation in a solid state after the step (a). (C) a step of adding and introducing a transesterification catalyst and methanol to the residue of step (b) to perform a transesterification reaction to obtain dimethyl terephthalate and ethylene glycol, and then separating and recovering both.

[0015]

DETAILED DESCRIPTION OF THE INVENTION The polyester waste to which the present invention is directed is a mixture consisting essentially of natural fibers and polyalkylene terephthalate, wherein "substantially" means the natural fibers and Polyalkylene terephthalate is 50 wt% based on total polyester waste
If less than this, it means that the method of the present invention is not targeted.

In the recovery method of the present invention, it is necessary to sequentially pass the polyester waste through the above-mentioned steps (a) to (c). Hereinafter, each step will be described.

In the step (a), the polyester waste is heated at a temperature of 110 to 210.degree.
Need to put in. Here, the temperature of the EG is 11
If the temperature is lower than 0 ° C., the depolymerization time becomes extremely long, and it becomes inefficient. On the other hand, when the temperature exceeds 210 ° C., the thermal decomposition of the natural fiber becomes remarkable, and the quality of the recovered product is deteriorated. The preferable range of the temperature is 140 to 190 ° C when vegetable fibers are contained as natural fibers, and 110 to 140 ° C when animal fibers are contained as natural fibers. If the amount of the catalyst is too large, it is not economical.
%, And under these conditions, 1 to 10% by weight.
Hold for a long time.

Further, the weight ratio of EG and polyalkylene terephthalate to be supplied to the step (a) is preferably set to about 0.5 to 20, and when the ratio is within this range, the shape of the polyester waste is reduced. For this reason, the depolymerization time does not change significantly, and the purification cost of EG finally reused can be suppressed. The weight ratio is 1 to
It is preferably set to 5.

The contact between the polyester waste and the EG and the temperature rise of the polyester waste include stirring in the melting tank,
The combined use of operations such as circulation of the liquid in the tank by an external pump can also have the effect of shortening the melting time, but excessive stirring will waste power and the liquid in the tank will flow. That is enough.

Next, in step (b), step (a)
It is necessary to carry out solid-liquid separation of the polyester waste which has passed through. The polyester waste forms a slurry state, and various solid-liquid separation devices can be used for solid-liquid separation of the slurry, and the purpose is to remove foreign matter when natural fiber is little mixed. A filter may be used.

The polyester waste obtained by the operation of the step (b) is concentrated by concentrating a liquid containing the oligomer until the weight ratio of EG and polyester waste becomes 0.5 to 2.0 based on the raw material charge ratio. Is preferred.

The means for concentrating the oligomer-containing EG solution can be easily carried out by a distillation operation, which must be carried out under reduced pressure. The boiling point of the EG used, the thermal decomposition temperature of the natural fiber In consideration of the fact that the temperature rises at 140 ° C. or higher, and the fact that natural fibers that have become fine particles by the solid-liquid separation operation leak in, the pressure is reduced to 1.33 to 100 kpa, preferably 1.33 to 6.7 kpa. Preferably, a distillation operation is performed.

Finally, in the step (c), the transesterification catalyst and MeO 2 are added to the separated solution of the step (b), preferably to a solution in which the oligomer is concentrated to the above-mentioned ratio.
H is added and added to carry out transesterification, and DMT
After obtaining EG and EG, they are separated and recovered.

In the transesterification reaction, 200 to 400% by weight of MeOH is charged based on the polyester waste, and at the same time, the transesterification catalyst is charged at 1 to 10% by weight based on the polyester waste. The pressure in the transesterification reaction tank may be near atmospheric pressure, and the transesterification reaction temperature may be 65-85 ° C. for the reaction to proceed.

The transesterification is completed in 0.5 to 5 hours, and a solid slurry of DMT, MeOH and EG is obtained. In recovering DMT from the slurry,
Although a solid-liquid separation device can be applied as a conventional means, any method may be employed.

A small amount of DMT is dissolved in MeOH and EG to form a slurry, and the slurry is cooled and then supplied to a solid-liquid separator. The cake of DMT obtained by the solid-liquid separation operation is MeO as a mother liquor.
H and EG, the cake is made of new MeO
H, stirred and slurried again to wash DMT. The obtained slurry is again supplied to the solid-liquid separation device, where it is separated into DMT cake and mother liquor MeOH.

The number of repetitions of this washing operation is determined uniquely by the required quality of the DMT to be recovered.
Four operations may be performed. In addition, the mother liquor MeOH in each washing step can be circulated as usual. Further, the washing operation may be performed continuously or batchwise.

EG and Me separated from DMT by solid-liquid separation
The mixture with OH contains dissolved DMT, a depolymerization catalyst and a transesterification catalyst, and EG and MeOH are separated and purified respectively for use in the process again. This purification operation is preferably performed by distillation, but need not be limited to the distillation operation. In the case of performing distillation, MeOH having a low boiling point is first distilled off, and the liquid remaining at the bottom of the column is supplied to the next distillation column to remove EG. At this time,
Since DMT dissolved in EG, catalyst and oligomers having 1 to 3 repeating units are present at the bottom of the column, a part of the bottom liquid is used for the purpose of reducing the amount of catalyst used and improving the recovery rate of active ingredients. May be returned to the depolymerization tank.

The DM recovered by the solid-liquid separation operation described above
Since there is a possibility that a small amount of solid matter such as dust and sand contained in the polyester waste may be mixed into T, depending on the required quality of DMT, it may be purified by vacuum distillation if necessary. A part of the bottom liquid in the purification operation may be returned to the depolymerization tank.

Hereinafter, the recovery method of the present invention will be described more specifically with reference to a flowchart (FIG. 1) showing one embodiment of the recovery method of the present invention.

First, pulverized polyalkylene terephthalate, depolymerization catalyst and EG are simultaneously charged into a depolymerization tank (1 in the figure) to depolymerize polyester waste.

Natural fibers that do not dissolve in the EG in the depolymerization tank (1 in the figure) can be separated by a solid-liquid separation device (2 in the figure), and are removed outside the system as solids. The solids are further washed with EG in a washing tank (3 in the figure), and the deposits on the surface of the solids are circulated to a depolymerization tank (1 in the figure), and the solids are separated as natural fibers. can do. Here, the residence time of the depolymerization tank may be 1 to 10 hours, and the internal temperature may be 110 to 190 ° C.

Next, the alkylene terephthalate after the completion of the depolymerization reaction is distilled and distilled in a distillation / concentration tank (4 in the figure) so that the EG and the polyester waste are in a charge weight ratio of 0.5 to 2. The removed and distilled EG can be circulated and supplied to a depolymerization tank (1 in the figure).

Next, the concentrated polyester waste depolymerized solution is supplied to a transesterification reaction tank (5 in the figure).
By supplying the transesterification catalyst and MeOH, the polyester waste depolymerized solution is converted into DMT and EG. At this time, the temperature in the transesterification reactor was 65 to 8
It is preferable to have a capacity of 0.5 to 5 hours at 5 ° C. and normal pressure.

The generated DMT and EG are in excess MeOH.
Then, the mixture is supplied to a solid-liquid separator (6 in the figure) to be separated into DMT cake, EG and MeOH.
Here, since the DMT cake contains MeOH as a mother liquor, it is again slurried with MeOH (not shown) and solid-liquid separated again.

Further, the cake of DMT washed twice is added to D
The purified DMT is supplied to an MT distillation column (7 in the figure) and recovered. Part of the bottom at the bottom of the distillation column (7 in the figure) is returned to the depolymerization tank (1 in the figure), and the remainder is discarded outside the system.

On the other hand, a mixed solution of EG and MeOH separated by a solid-liquid separation device (6 in the figure) is subjected to a MeOH distillation column (8 in the figure).
And MeOH is distilled off. This distilled MeOH can be used as a part of the MeOH supplied to the transesterification reaction tank (5 in the figure).

Further, the residue at the bottom of the MeOH distillation column (8 in the figure) is supplied to an EG distillation column (9 in the figure) to distill EG. Part of the distilled EG is used as EG to be supplied to a depolymerization tank (1 in the figure), and the remaining EG is recovered and taken out of the system.

A part of the bottom of the distillation column (9 in the figure) is returned to the depolymerization tank (1 in the figure), and the rest is discharged out of the system as waste.

By performing the above operations, DMT and EG as active ingredients were converted from polyester waste substantially consisting of natural fibers and polyalkylene terephthalate.
Can be easily collected.

[0041]

EXAMPLES Hereinafter, the content of the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto. In addition, each numerical value in an Example was calculated | required by the following method. In the examples, “parts” means “parts by weight” unless otherwise specified.

(1) Content of dimethyl terephthalate, monohydroxyethyl terephthalate, bishydroxyethyl terephthalate (%): DMT contained after depolymerization, DMT contained in liquid before and after distillation,
Monohydroxyethyl terephthalate (hereinafter may be abbreviated as MHET) contained in the distillation still residue,
And bishydroxyethyl terephthalate (hereinafter referred to as BH
ET) may be subjected to gas chromatography (HP-5890, manufactured by Hewlett-Packard Company, capillary column: TC-17, manufactured by GL Sciences Inc.).
01 use).

(2) EG content (%): The amount of EG contained after depolymerization and the amount of EG contained in the liquid before and after distillation were analyzed by gas chromatography (GC-7A, manufactured by Shimadzu Corporation, Packing column filler: using polyethylene glycol 6000 manufactured by GL Sciences Corporation).

(3) Oligomer weight average molecular weight: Polyalkylene terephthalate in a partially depolymerized and molten state was used as a sample and subjected to liquid chromatography (manufactured by Hitachi, Ltd.).
L-4000), using tetrahydrofuran as a mobile phase and a mixed solvent of hexafluoro-2-propanol and chloroform as a sample solvent, the molecular weight was determined by a calibration curve prepared using standard polystyrene.

Example 1 399.7 parts of EG was charged into a separable flask, and a fibrous mixed fabric (commercial product of 65% polyester and 35% cotton) was cut.
2 parts and 1.5 parts of sodium carbonate were added, and the mixture was kept at 185 ° C. for 4 hours with stirring.

The above-mentioned EG solution was charged into a filtration device using a 100-mesh wire gauze whose surroundings were heated to 170 ° C. as a filter material, and hot filtration was performed. The natural fibers remaining on the filter were washed with 90 parts of EG heated to 170 ° C., and the washing liquid was received in another receiver.

The EG solution obtained by hot filtration was 6.7 kpa
And 309 parts of EG were recovered as a fraction.

To this concentrated liquid, 5.55 parts of sodium carbonate and 136.2 parts of MeOH were added as a transesterification catalyst. The liquid temperature was maintained at 75 ° C. under normal pressure with stirring for 1 hour to carry out a transesterification reaction.

The resulting mixture of DMT, EG and MeOH was cooled to 40 ° C. and filtered through a glass 3G-4 filter. 18 DMT collected on the filter
It was poured into 0 parts of MeOH, washed with stirring at 40 ° C., and filtered again with a glass filter. This operation was repeated twice.

DMT captured on the filter was charged into a distillation apparatus, and DMT was distilled off as a fraction by distillation under reduced pressure at a pressure of 6.7 kpa to collect 17.1 parts. DMT was recovered in an amount of 54.5% by weight based on the charged polyester. There was no problem with the quality of distilled DMT.

[Comparative Example 1] The same operation as in Example 1 was carried out except that the temperature of the depolymerization was changed to 230 ° C. As a result, the obtained DMT was colored and a problem in quality was clearly recognized. Was.

[0052]

According to the method of the present invention, DMT and EG can be easily recovered from polyester waste substantially consisting of natural fibers and polyalkylene terephthalate.

[Brief description of the drawings]

FIG. 1 is a flowchart schematically showing one embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Depolymerization tank 2 Solid-liquid separation device 3 Washing tank 4 Distillation / concentration tank 5 Ester exchange reaction tank 6 Solid-liquid separation device 7 DMT distillation column 8 MeOH distillation column 9 EG distillation column 10 Pulverized polyester waste 11 Depolymerization catalyst 12 MeOH 13 Transesterification catalyst 14 Recovered DMT 15 Recovered EG 16 Natural fiber solids 17 Waste 18 Waste

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C07C 69/82 C07C 69/82 A C08J 11/16 C08J 11/16 // C08L 67:00 C08L 67:00 (72) Inventor Minoru Nakajima 77, Kitayoshida-cho, Matsuyama-shi, Ehime Pref. In Teijin Limited Matsuyama Office (72) Inventor Kazuhiro Sato 77, Kitayoshida-cho, Matsuyama-shi, Ehime Pref. 4F301 AA25 AB03 CA09 CA23 CA32 CA33 CA41 CA61 CA64 CA65 CA68 CA71 CA72 CA73 4G069 AA02 AA08 BB04A BB16A BB16B BC01A BC02B BE08A CB35 DA05 EA01Y 4H006 AA02 AC48 AC91 AD11 AD17 BA02 BA06 BS30 FE12

Claims (14)

[Claims] 1. A method for separating and recovering an active ingredient from a polyester waste substantially consisting of a natural fiber and a polyalkylene terephthalate, wherein the waste comprises the following (a) to
A method for recovering an active ingredient from polyester waste, comprising sequentially passing through each step of (c) to separate and recover dimethyl terephthalate and alkylene glycol as active ingredients. (A) A step of charging polyester waste into ethylene glycol containing a depolymerization catalyst at a temperature of 110 to 210 ° C. (B) a step of removing the natural fiber by solid-liquid separation in a solid state after the step (a). (C) a step of adding and introducing a transesterification catalyst and methanol to the residue of step (b) to perform a transesterification reaction to obtain dimethyl terephthalate and ethylene glycol, and then separating and recovering both. 2. The separation and recovery method according to claim 1, wherein the separation and recovery in the step (c) is performed by distillation or solid-liquid separation operation. 3. The depolymerization catalyst used in the step (a) is at least one selected from the group consisting of alkali metal carbonates and oxides, alkaline earth metal carbonates and oxides, manganese acetate and zinc acetate. Kinds of compounds, and the added amount is 0.1 to 10 based on the weight of the polyester waste.
%. 4. The amount of ethylene glycol used in step (a) is adjusted to 0.5 based on polyalkylene terephthalate.
The separation and recovery method according to claim 1, wherein the weight is 20 to 20 times by weight. 5. The method according to claim 1, wherein the solid separated in the step (b) is further washed with ethylene glycol to separate and remove the active ingredient adhering to the natural fiber. 6. The residue obtained after removing the solid matter in the step (b) is distilled and concentrated, and the distilled ethylene glycol is recycled and reused in the step (a), and the distillate is sent to the next step. The separation and recovery method according to claim 1. 7. A distillation / concentration operation wherein the weight ratio of the weight obtained by subtracting the natural fibers separated in step (b) from the polyester waste charged in the depolymerization tank to the weight of ethylene glycol is 0.5 to 2. The recovery method according to claim 6, wherein the method is performed so as to fall within the range. 8. A distillation / concentration operation of 1.33 to 100 kp
The method according to claim 6, wherein the method is performed under the pressure of a. 9. The method according to claim 1, wherein the polyalkylene terephthalate is polyethylene terephthalate. 10. The method according to claim 1, wherein the natural fiber is cotton. 11. The method according to claim 1, wherein the natural fiber is hemp. 12. A method for reusing an active ingredient, wherein the recovered dimethyl terephthalate according to claim 1 is used as a raw material for producing terephthalic acid. 13. A method for recycling an active ingredient, wherein the recovered dimethyl terephthalate according to claim 1 is used as a raw material for producing bis (β-hydroxyethyl) terephthalate. 14. A method for reusing an active ingredient, wherein the recovered dimethyl terephthalate according to claim 1 is used as a raw material for producing a polyester.